1. Field of the Invention
The present invention relates generally to communication and control systems for use in monitoring and controlling various systems and equipment in industrial environments.
2. Background Art
At locations where oil and gas are produced, a number of flammable gases may be present, including mixtures of oxygen, methane, ethane, propane, hydrogen sulfide and others. Similar potentially dangerous environmental conditions exist in locations in which petroleum products are being recovered, refined or processed. Likewise, in industrial areas where large quantities of dust are present, such as in grain handling facilities or pulp and paper mills, hazardous environmental conditions may exist. Standardized classifications for the various types of hazardous locations have been adopted and assigned by regulatory agencies according to the nature and type of hazard that is generally present or that may occasionally be present.
Because electrical components, by their nature, may generate heat and sparks sufficient to ignite a flammable gas or other flammable mixture under even normal operating conditions, such components must be carefully selected and installed when used in an area that is classified as hazardous. More specifically, the components must exceed certain minimum standards as to such characteristics as power consumption, operating temperature, current and voltage requirements, and energy storage capabilities. These standards are also established by regulatory authorities and vary depending upon the particular hazardous environment.
Certain electrical devices are intrinsically safe. An intrinsically safe device may be generally described as a device that during normal operation, as well as operation during any fault condition, cannot cause a spark or achieve a temperature sufficient to ignite the gas or other substance that is present and that causes the area to be classified. If a device is not intrinsically safe, other means must be provided to ensure that the device cannot serve as a source of ignition. Typically where a device is not intrinsically safe, it may be made safe by housing it in an explosion-proof enclosure or housing. An explosion-proof housing or enclosure, as that term is used herein, means an enclosure that prevents any spark or explosion within the enclosure from causing the atmosphere outside the housing to ignite.
Although areas that are classified as hazardous are prevalent in many industries, the problems of powering and communicating with electrical devices in hazardous areas are particularly acute in the production, gathering, distribution and transportation of oil and gas. Many of the areas around an oil and gas production site are classified as hazardous, and thus special precautions are required with respect to the electrical communication and power distribution systems. To efficiently and safely control the operation, a system having sensors positioned in a number of locations in the hazardous area is often required. These sensors will transmit needed data to a computer which can process that data and transmit important information to the operator by means of a console or monitor. By viewing the information on the monitor, the operator can then make whatever changes that are appropriate to the system to assure safe and efficient operation.
The monitor is typically required to be very close to the well head and thus is located in a hazardous area. Historically, such consoles have varied with respect to the amount of information displayed and type of indicators used. In the past, when a simple meter or gage provided all the information that was required, the device could sometimes be made intrinsically safe. However, due to the sophistication of today's oil and gas production operations, consoles or monitors usually provide an operator with a tremendous amount of information. Additionally, the console may permit the operator to issue commands or make inquiries through the use of a keyboard or key pad, and may display all the needed information by means of an LCD or other display. These modern consoles or monitors typically have a substantial power requirement that has prevented them from being made intrinsically safe, and often requires that they be housed in an explosion proof enclosure.
In oil and gas production operations, various sensors, consoles and monitors are used in remote areas where running power lines is difficult. Thus, it is often desirable to power such units with solar power or batteries. Because such power sources have limited capacities, it would be advantageous to develop low power consumption components for these units.
Another approach to increasing the working life of a power source is to shut down non-essential units when not in use, and run components only to the extent necessary to perform desired functions (e.g. running a microprocessor at a lower clock speed or turning off a display when not in use). However, this task is made difficult in a hazardous area because methods of regulating power to the system, and configuring operating ranges of components, are limited. For instance, a typical toggle switch cannot be used in such an area, due to its electrical characteristics. Therefore, it would be advantageous to develop a power control system that may be used safely in a hazardous area, so that electrical components (e.g., a visual display, microprocessor, or infrared data link) can be regulated to consume minimal power. This avoids unnecessary consumption of power.